This project is concerned first with identifying the functions of the cell types in the hypophyseal pars distalis by using experimental procedures combined with histochemical and immunohistochemical staining and electron microscopy. Special emphasis is being placed on clarifying the cellular origin of FSH and LH in rats and primates. Since immunohistochemical staining allows reasonable certainty in determination of cell function, the influence of naturally occurring gonadal, adrenocortical and pituitary hormones on the hypophysis is being studied. Second, using primarily immunohistochemical methods, the direct and indirect action of oral contraceptive agents on the hypophysis is under investigation. Third, immunohistochemistry is being used to analyze the influence of hypothalamic hormones on secretory activity of pituitary cells in culture.